Original Article A Crossover Analysis of Mandatory Minute Ventilation Compared to Synchronized Intermittent Mandatory Ventilation in Neonates Scott O. Guthrie, MD Chris Lynn, RRT Bonnie J. LaFleur, PhD Steven M. Donn, MD William F. Walsh, MD BACKGROUND: Mandatory minute ventilation (MMV) is a novel ventilator mode that combines synchronized intermittent mandatory ventilation (SIMV) breaths with pressure-supported spontaneous breaths to maintain a desired minute volume. The SIMV rate is automatically adjusted to maintain minute ventilation. OBJECTIVE: To evaluate MMV in a cohort of infants without parenchymal lung disease alternately ventilated by MMV and SIMV. DESIGN/METHODS: Neonates >33 weeks’ gestational age and electively intubated for medical or surgical procedures were enrolled. Exclusionary criteria included: nonintact respiratory drive or active pulmonary disease. Infants were randomized to receive 2 hours of either SIMV or MMV and then crossed over to the other mode for 2 hours. Ventilator parameters and end-tidal CO 2 (etCO 2 ) were measured via inline, mainstream monitoring and recorded every minute. RESULTS: In total, 20 infants were evaluated. No statistically significant differences were found for overall means between etCO 2 , minute volumes, peak inspiratory pressure (PIP), or positive end expiratory pressure (PEEP). However, there was a significant difference in the type of ventilator breaths given and in the mean airway pressure. Additionally, there was a statistically significant negative trend in MMV over time compared to SIMV, although this was subtle and could have been due to extreme cases. CONCLUSIONS: Neonates with an intact respiratory drive can be successfully managed with MMV without an increase in etCO 2 . While this mode generates similar PIP and PEEP, the decrease in mechanical breaths and the mean airway pressure generated with MMV may reduce the risk of some of the long-term complications associated with mechanical ventilation. Journal of Perinatology (2005) 25, 643–646. doi:10.1038/sj.jp.7211371; published online 4 August 2005 INTRODUCTION Mandatory minute ventilation (MMV) is a mode of ventilation that combines features of synchronized intermittent mandatory ventilation (SIMV) and pressure support ventilation (PSV). This mode of ventilation is theoretically a more intuitive approach to ventilator management. In MMV the mandatory ventilator rate is varied based upon the patient’s needs rather than delivering a constant preset rate. In MMV, the clinician chooses a minimum minute volume (the product of tidal volume and frequency) for the patient. If the patient’s spontaneous breathing, which is augmented with PSV, meets or exceeds this minute volume, no mandatory ventilator breaths are provided. If, however, the patient’s minute volume falls below the preselected minimum, the ventilator will provide ‘‘catch up’’ breaths at a fixed frequency to ensure that the patient receives this preselected minute ventilation. This mode was first described in the adult literature in 1977 and has been shown to be successful in ventilator weaning. 1,2 Advances in microprocessor technology have recently allowed this mode to be adapted to neonatal ventilators. Its use in the newborn was first reported by Donn and Becker. 3 There are, however, no clinical studies to evaluate the use of this mode in neonates. The purpose of this study was to compare MMV and SIMV with respect to carbon dioxide removal and other ventilator parameters using a crossover design. The null hypothesis was that there would be no differences in carbon dioxide removal or other ventilatory parameters in infants alternately ventilated with MMV or SIMV. METHODS Patient Inclusion Criteria Infants were eligible for the study if they were >33 weeks’ gestational age by obstetrical dating criteria. Infants who were Address correspondence and reprint requests to Scott O. Guthrie, MD, Department of Pediatrics, Division of Neonatology, Vanderbilt University Medical Center, A-0126 MCN, Nashville, TN 37232-2370, USA. Department of Pediatrics (S.O.G., C.L., W.F.W.), Division of Neonatology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Biostatistics (B.J.L.), Vanderbilt University School of Medicine, Nashville, TN, USA; and Department of Pediatrics (S.M.D.), Division of Neonatal-Perinatal Medicine, University of Michigan Health System, Ann Arbor, MI, USA. Journal of Perinatology 2005 25:643–646 r 2005 Nature Publishing Group All rights reserved. 0743-8346/05 $30 www.nature.com/jp 643